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The SEDs of Interacting Galaxies. NGC 520: NUV, 3.6 µ m , & 8.0 µ m. Lauranne Lanz Nicola Brassington , Andreas Zezas , Howard A. Smith, Matthew L. N. Ashby, Elisabete da Cunha, Christopher Klein, Patrik Jonsson , Chris Hayward Lars Hernquist , Giovanni Fazio
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The SEDs of Interacting Galaxies NGC 520: NUV, 3.6 µm, & 8.0 µm Lauranne Lanz Nicola Brassington, Andreas Zezas, Howard A. Smith, Matthew L. N. Ashby, Elisabeteda Cunha, Christopher Klein, PatrikJonsson, Chris Hayward Lars Hernquist, Giovanni Fazio Harvard-Smithsonian Center for Astrophysics llanz@cfa.harvard.edu L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Outline • What is Spitzer Interacting Galaxy Survey (SIGS)? • SED shapes • SED fitting • sSFR comparisons • Trends with interaction stage N3226-N3227 3.6 µm, 4.5 µm, & 8 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Sample Selection • Keel-Kennicutt(Keel et al. 1985) “complete” and “Arp” samples: • Selected based on association likelihood • Require |Δv|< 600 km s-1 to remove non-associated pairs • Imposed distance constraint cz < 4000 km s-1 • Resulting sample: 111 galaxies in 50 systems NGC 2976: NUV, 3.6 µm, & 8.0 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Observations • Complete Spitzer coverage: • IRAC, MIPS, and nuclear IRS spectra • Almost complete GALEX coverage • Some Herschel coverage • Ancillary data • WISE coverage • Some Chandra/XMM coverage • Hα fluxes M51 NUV, IRAC 3.6 µm, & SPIRE 250 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Sample Selection and Observation Set Benefits • Not morphologically selected: large range of interaction parameters • Not infrared selected: less active systems included • Not based on optical line diagnostics • UV and IR coverage gives complete SFR NGC 520: NUV, 3.6 µm, & 8.0 µm NGC 470 & NGC 474: FUV, 3.6 and 4.5 µm, & 8.0 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Example: M51 and NGC 3430/3424 IRAC 3.6 µm, 4.5 µm, 8 µm 2MASS J, H, Ks GALEX FUV NUV SPIRE 250 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Photometry • S-Extractor used to determine NUV and 3.6 µm apertures IRAC 3.6 µm, 4.5 µm, 8 µm 2MASS J, H, Ks GALEX FUV NUV SPIRE 250 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Photometry • S-Extractor used to determine NUV and 3.6 µm apertures • Fluxes determined in larger aperture in all bands • Uncertainty: Calibration and Poisson IRAC 3.6 µm, 4.5 µm, 8 µm 2MASS J, H, Ks GALEX FUV NUV SPIRE 250 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
SED shapes M51 A M51 B Log( νLν / L) Log( νLν / L) NGC 3424 NGC 3430 Log( νLν / L) Log( νLν / L) L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Two blackbodies + β=1.5 graybody M51 A M51 B 4367 K 356.2 K 28.6 K 4058 K 357.1 K 25.8 K Log( νLν / L) Log( νLν / L) NGC 3424 NGC 3430 3572 K 303.5 K 29.2 K 3307 K 339.5 K 25.2 K Log( νLν / L) Log( νLν / L) L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
MagPhys SED-fitting Code • Optical stellar from Bruzual & Charlot 2003 and infrared dust from da Cunha, Charlot, & Elbaz 2008 spectral libraries • Energy absorbed in UV/optical is re-emitted in IR • No AGN contribution considered • Likelihood distributions constructed for model parameters to determine best fit SED Elisabeteda Cunha’s talk this afternoon L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Fit SEDs sSFR Log( λLλ / L) Tcold Twarm sSFR Log( λLλ / L) Tcold Twarm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Fit SEDs sSFR Log( λLλ / L) Tcold Twarm sSFR Log( λLλ / L) Tcold Twarm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Fit comparisons TWarm FIR β=1.5 gray-body temperature falls between SED-fitted warm and cold temperatures TSED / K TCold TGraybody/ K Frac. Difference Log( L8-1000µm,3part/ L) Log( LDust,SED / L) The integrated 8-1000 µm 3-component fit agrees well with the dust luminosity determined from fitting the SED. L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Comparison of Specific Star Formation Rates N 3430 M51A Log(sSFR/yr-1) Prescription Log(sSFR/yr-1) SED Fitting L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Trends with Interaction Stage L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Trends with Interaction Stage L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Trends with Interaction Stage L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Summary • SIGS will provide a sample of interacting galaxies from first pass to coalescence with a range of interaction parameters. IC 1801 and NGC 935 NUV, 3.6 and 4.5 µm, & 8.0 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Summary • With the first 10 groups with SPIRE data, we: • find a range of SED shapes, especially in the ratio of MIR to optical/UV. • measured sSFR and temperatures using the MagPhys (da Cunha et al. 2008) SED-fitting code. • find an increase in warm component temperature with interaction stage, but no significant change in sSFR. M81: NUV, 8.0 µm, & 250 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Thank you for the attention and stay tuned for more: • 40 more interacting groups • Nuclear activity • Comparison with simulated systems M101: NUV, 3.6 µm, & 8 µm Cox et al. 2006 N3448 – U6016: FUV, 3.6 µm, 4.5 µm, & 8 µm L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011